SimpleTimes
The absolute times start a job only once. They are therefore suitable for one-off actions, such as taking over the inventory of a warehouse.
The relative times start the job on the specified days of the week and are therefore suitable for recurring tasks.
(1) Use the context menu to create absolute entries for 08.01.2018, 08:00, 08.01.2018, 08:30 and 08.01.2018, 11:30
(2) and relative entries for Monday, 08:45 and Monday, 10:45.
The following figure shows an excerpt of the chronological progression for Monday, 08.01.2018.
(1) A job is started by the absolute scheduling.
(2) A job is started by the relative scheduling.
If a job is already running at a start time, the additional start will be skipped. This applies to relative and absolute scheduling. The following figure shows such a case.

(1) A job is started by the absolute scheduling.
(2) Since there is still a job running, no new job is started.
(3) A job is started by the relative scheduling.
(4) Since there is still a job running, no new job is started.